1. Field of the Invention
The present invention generally relates to a beam projector, and more particularly, to a focusing device for a subminiature beam projector, which is mountable on a small-size device, such as a portable terminal.
2. Description of the Related Art
A beam projector is any device that includes a light source, a liquid crystal panel, and a lens, in which light emitted from the light source goes through the liquid crystal panel and an image displayed on the liquid crystal panel is projected onto a screen. The number of liquid crystal panels or the number of lenses on the beam projector may vary.
The beam projector can project on a large screen compared to its size, and thus has been used variously in conferences, shows, or the like. Recently, with the wide use of portable terminals such as mobile communication terminals, a portable terminal having a subminiature beam projector mounted therein has been commercialized. A portable terminal having a beam projector mounted therein is useful to workers who engage in frequent business trips or conferences.
A beam projector mounted in a compact device, such as a portable terminal, usually has mounted therein a focusing device using a focusing knob such as a dial. A user manipulates the focusing knob to advance or retreat a body tube having a plurality of lens mounted therein in an axial direction. Thus, the focusing knob has to be positioned adjacent to the body tube and be so exposed as to allow the user to manipulate the focusing knob in an outer portion of the device.
Thus, when the beam projector is installed in a compact device such as a portable terminal, the focusing knob limits the installation position of the beam projector. In a compact device having a small part-mounting space, such a problem is a serious constraint on selecting a part-mounting structure. As a result, the conventional beam projector including the focusing device is difficult to mount in a compact device such as a portable terminal.